Reporting Segments - Total assets and investments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information
Assets	$ 119,950	$ 112,249
Investments	88,362	81,260
Property-Liability
Segment Reporting Information
Assets	67,243	61,947
Investments	48,414	43,634
Service Businesses
Segment Reporting Information
Assets	5,746	5,473
Investments	1,544	1,203
Allstate Life
Segment Reporting Information
Assets	14,771	13,613
Investments	11,914	10,809
Allstate Benefits
Segment Reporting Information
Assets	2,915	2,822
Investments	1,941	1,809
Allstate Annuities
Segment Reporting Information
Assets	26,914	26,798
Investments	22,221	22,336
Corporate and Other
Segment Reporting Information
Assets	2,361	1,596
Investments	$ 2,328	$ 1,469